There is a conventionally known laser lift-off apparatus that irradiates a carrier on which a material layer is laminated with a square laser spot to locally heat the carrier and delaminate the material layer from the carrier. The laser lift-off apparatus uses a square laser spot. The laser spot has a profile having a central portion where the laser intensity is uniform and a peripheral portion where the laser intensity gradually decreases. Adjacent irradiation positions are determined so that the peripheral portions of the laser spots overlap with each other, and the laser spot is applied in the form of pulses in the irradiation positions (see Patent Literature 1, for example).
On the other hand, there is a known laser irradiation apparatus that irradiates a substrate with a linear laser spot. The linear laser spot has, along the major axis of the linear laser spot (the laser spot axis extending in the length direction and passing through the center of the width of the laser spot), a profile having a flat portion where the laser intensity can be considered to be uniform and peripheral portions where the laser intensity gradually decreases and, along the minor axis of the linear laser spot (the laser spot axis extending in the width direction and passing through the center of the length of the laser spot), a profile having a roughly Gaussian distribution (see Patent Literature 2, for example).